In this Issue:

Invasive Species

During
the past two centuries, invasive species have significantly
changed the Great Lakes ecosystem. In turn, the changes have had broad
economic
and
social effects on people that rely on the system for food, water,
and recreation.

An "invasive species" is a plant or animal that is non-native
(or alien) to an ecosystem, and whose introduction is likely to cause
economic, human health, or environmental damage in that ecosystem. Once
established, it is extremely difficult to control their spread.

At least 25 non-native species of fish have entered the Great Lakes
since the 1800s, including round
goby, sea
lamprey, Eurasian ruffe, alewife and
others. These fish have had significant impacts on the Great Lakes food
web by competing with native fish for food and habitat. Invasive animals
have also been responsible for increased
degradation of coastal wetlands; further degrading conditions
are resulting in loss of plant cover and diversity.

Zebra Mussels

Non-native
mussels and mollusks have also caused turmoil in the food chain. In 1988, zebra
mussels were inadvertently introduced to Lake St. Clair,
and quickly spread throughout the Great Lakes and into many inland lakes,
rivers,
and canals. Since then, they have caused severe problems at power plants
and municipal water supplies,
clogging intake screens, pipes, and cooling systems. They have also nearly
eliminated the native clam population in the ecosystem.

The spiny
water flea(Cercopagis pengoi) was the most
recent species to enter the Great Lakes.
This organism, a native of Middle Eastern seas, is a tiny predatory crustacean
that
can reproduce
both sexually and, more commonly, parthenogenically (without fertilization).
This allowed them
to quickly populate Lake Ontario.

Some of these plants are prolific seed producers, which
allows them to spread rapidly over large areas. Invasive
purple loosestrife, for example, are 2-3 meters
tall and can produce 2.7 million seeds
each year. Others reproduce from fragments of root
or rhizome, which hinders removal and control. All have become established
quickly in
the Great Lakes, displacing the native plant populations that support
wildlife habitat and prevent erosion. Their prevalence in recreational
waters also hinders swimming and boating.

In the St. Lawrence River, studies have found that disturbances
by boat or fish may facilitate the spread of common reed, a very persistent
invasive plant. Dense beds of common
reed may threaten local fish and bird habitats.

To
prevent and control additional invasions in the Great Lakes, coordinated
efforts are under way by U.S. and Canadian governments, eight state
governments, two provincial
governments, and regional and local programs.

Ballast Water Regulation

Ballast water is taken onto or discharged from a ship
as it loads or unloads its cargo, to accommodate changes in its weight.

Thirty percent of invasive species have been introduced in the Great
Lakes through ballast
water.
In the
early
1990's,
the
U.S. Coast
Guard began
requiring
ships
to exchange their ballast water, or seal their ballast tanks for the
duration of their stay. The Coast Guard later used their success in the
Great Lakes to develop a ballast management program for
the entire nation. Currently, the Coast Guard is in the process of
developing ballast water discharge standards.

Preventing Potential Invaders

Man holding large Asian carp

Based
on the problems caused by non-native species, scientists are also
closely watching other species that have invaded nearby ecosystems. Asian
carp are of particular concern because they have been found
in nearby waterways that eventually connect to the Great Lakes. In 2004,
EPA and other state and local agencies began construction of a permanent
electric barrier to prevent the fish from entering Lake Michigan (more
about the barrier).

EPA is also studying how existing invasive species have become established
in the Great Lakes. These studies will help develop new techniques
to predict
future
invasions.